Crackdown Upends Cambodia Labor Movement's Show of Strength

PHNOM PENH, Cambodia—The violent crackdown this month on Cambodia's largest-ever garment strike points to how seriously Prime Minister Hun Sen deems the threat of labor unions joining forces with the country's opposition movement that is fervently challenging his long hold on power.

Tens of thousands of workers in Cambodia's largest export industry walked out Dec. 24. After 10 days of protests, police fired on a crowd of striking workers, killing at least four people and injuring dozens. Authorities arrested 23 people...